CVE-2026-42235

Description

n8n is an open source workflow automation platform. Prior to versions 1.123.32, 2.17.4, and 2.18.1, an unauthenticated attacker could register a malicious MCP OAuth client with a crafted client_name. If a victim user authorized the OAuth consent dialog and a second user subsequently revoked that access, a toast notification would render the injected script. Clicking the link would execute arbitrary JavaScript in the victim's authenticated n8n browser session, enabling credential and session token theft, workflow manipulation, or privilege escalation. This issue has been patched in versions 1.123.32, 2.17.4, and 2.18.1.

CVSS v3.1 Score

9.6

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

EPSS — Exploit Prediction

0.0008

Probability of exploitation

0.24%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-79 Cross-site Scripting (XSS)

CWE-87 CWE-87

Affected Products

Vendor	Product	Versions
n8n	n8n	< 1.123.32
n8n	n8n	2.17.0 — 2.17.4
n8n	n8n	All

References

Advisories & Patches

https://github.com/n8n-io/n8n/security/advisories/GHSA-537j-gqpc-p7fq

Frequently Asked Questions

What is CVE-2026-42235? +

n8n is an open source workflow automation platform. Prior to versions 1.123.32, 2.17.4, and 2.18.1, an unauthenticated attacker could register a malicious MCP OAuth client with a crafted client_name. If a victim user authorized the OAuth consent dialog and a second user subsequently revoked that access, a toast notification would render the injected script. Clicking the link would execute arbitrary JavaScript in the victim's authenticated n8n browser session, enabling credential and session token theft, workflow manipulation, or privilege escalation. This issue has been patched in versions 1.123.32, 2.17.4, and 2.18.1. It has a CVSS v3.1 base score of 9.6 (CRITICAL).

How severe is CVE-2026-42235? +

CVE-2026-42235 has a CVSS v3.1 score of 9.6 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0008, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-42235? +

CVE-2026-42235 affects products from n8n, specifically: n8n. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-42235? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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